Dive summary:

• Facebook statement and research by PageLever dispute claims that Facebook altered its algorithm to encourage pages to pay to promote posts.
• The change in page reach was tied to Facebook adjusting EdgeRank in September to more aggressively punish pages that spam.
• PageLever found that the number of fans that pages are reaching as stayed consistent since July, but there has been a large change in standard deviation because of the EdgeRank adjustment.

From the article:

Will Cathcart, Facebook’s product manager for news feed tells me: “We made a relatively large ranking change in September that was designed to reduce spam complaints from users. We used [spam] reports at an aggregate level to find Pages or apps generating a lot of reports [and decrease their reach]. We’ve also added personalized attempts to reduce presence of posts you’re likely to complain about.”